feat: SEO altyapısı — pre-render, meta tags, blog posts, robots/sitemap

- vite-plugin-prerender yerine Playwright tabanlı post-build pre-render scripti
  (apps/web/scripts/prerender.mjs): 10 public route statik HTML'e dönüştürülüyor
- usePageMeta hook: her public route'da özgün title/description/canonical/OG tags
- index.html: favicon.svg, canonical, OG/Twitter Card, geliştirilmiş title+desc
- apps/web/public/: robots.txt, sitemap.xml (10 URL), favicon.svg
- nginx HSTS header eklendi (Strict-Transport-Security)
- Blog post sayfaları: blog_/$slug.tsx (4 tam yazı, 600-800 kelime)
- blog.tsx: post kartlarına Link eklendi
- Homepage: Schema.org JSON-LD (Organization + SoftwareApplication)
- Footer: placeholder href="#" sosyal linkler kaldırıldı
- deploy.sh + deploy.yml: playwright install chromium + prerender adımı

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/admin/admin.service.ts

@@ -17,6 +17,7 @@ import {
   referrals,
 } from "../database/schema/core";
 import { hashPassword } from "better-auth/crypto";
+import { generateReferralCode } from "@sase/shared";
 import { AnalyticsService } from "../analytics/analytics.service";
 
 @Injectable()
@@ -55,6 +56,7 @@ export class AdminService {
         email: data.email,
         emailVerified: true,
         role: data.role || "user",
+        referralCode: generateReferralCode(),
       })
       .returning({
         id: users.id,